The professor holds up a glass of water in class and asks students to guess its weight. When the students provide guesses, the professor notes that he doesn't actually know the weight unless he measures it. He then asks what would happen if he held the glass up for longer periods of time - minutes, hours, days. While the glass's weight would not change, holding it for long periods would cause strain, stress, and potential injury to the arm from fatigue. The professor explains that problems in life are similar - they at first seem manageable but can overwhelm us if dwelled on for too long. It's important to address challenges but also to "put them down" at the end of each day to avoid stress and